Synthetic tanning material



Patented Aug. 18, 1936 Alphons 0. Jaeger, Greentree, Pa.,

assignor to Cyanamid & Chemical Corporation, New York, N. Y., a corporation of Delaware No Drawing. Continuation of application Serial No. 715,163, March 12 1934. Division of application Serial No. 715,164, March 12, 1934. This application October 22, 1935, Serial No. 46,165

s Claim.

This invention relates to synthetic tanning agents of the sulfonic acid type and more specifically to those in which formic acid is used to produce at least a part ofthe, necessary acidification.

In my prior application, Serial No. 715,164, filed March 12, 1934, issued Feb. 4, 1936 as Patent No. 2,029,322, I have described tanning agents of the above type in which a number of organic acids including formic acid are used to produce the necessary low pH value for a most eflicient use of the synthetic tan. Briefly stated,'the tanning agents described in that application are prepared by sulfonating naphthalene or other aryl hydrocarbons, condensing with formaldehyde to pro; duce a disulfodiaryl methane tanning agent and substantially neutralizing by the addition of caustic soda or ammonium-hydroxide. Suflicient sulfuric acid is then added to liberate a portion 1 of the free sulfonic acid groups and an organic or inorganic acid is added to obtain a pH value of 0.5-2.0 which is the optimum range for synthetic tans of this type. The present application is a division of my. l l' or application above referred to and is directed specifically to the use of formic acid as the acidifying agent. Formic acid, when used as above described presents a number of advantages not found with other organic acids; it has a plumping action on the hides and gives a characteristic and highly desirable shade to the color of the finished leather. Moreover,,its low molecular weight and relatively high strength for an organic acid per-' mits obtaining the necessary low pH value in the tanning. solution without adding such a large quantity of acid as to injure the leather. Moreover, it possesses all the other desirable characteristics of'organic acids as a class, that is to say, it prevents corrosion and deterioration of 40 the leather by free sulfonic acid groups and produces a finished product of much better strength and appearance.

As has been stated, it is customary in the preparation of synthetic tanning agents of the di- 45 sulfodiaryl methane type to bring the formaldehyde condensate to neutrality, followed by acidification with sulfuric acid. This procedure may be followed in carrying out the present invention, for. I have found that thepresence of formic acid 50 is a synthetic tanning solution of this type inhibits the corrosive action of sulfuric and sulfonic acid groups on hides and leather to such an extent that it is possible to utilize these materials and thereby to obtain the extremely rapid tan- 5 ning and bleaching action which they exert without deterioration of the leather. Accordingly, it should be understood that the invention includes the use of formic acid in conjunction with synthetic tanning agents of the sulfonic acid type, either as the sole acidifying agent or in con- 5 Junction with other inorganic or organic acids.

This application is a continuation of my copending application Serial No. 715,163 filed March 12, 1934, issued Oct. 22, 1935 as Patent No. 2,017,863.

The invention will be further described in conjunction with the following speciflc example to which, however, it is not limited.

Example A sulfodinaphthyl methane tan is prepared by sulfonating naphthalene and condensing the product with formaldehyde. Any known procedures for obtaining this compound may be used such as for example described in U. S. Patent No. 1,336,759 to Schmidt, or the light-colored product described in Example I of my co-pending application Serial No. 715,164 filed March 12, 1934. As described in my co-pending application the product is brought to complete neutrality by the addition of caustic soda or ammonium hydroxide and sulfuric acid is added until a 10. cc. test sample requires 4 cc. of normal hydroxide for titration 'to neutrality to methyl red; Thereupon formic acid is added until 8 cc. of normal sodium hydroxide is required to neutralize a 10 cc. sample of the solution. The tan thus produced is admixed with approximately 50 pounds of sugar per thousand pounds of solution and 40 pounds of a suitable salt may be added, for example, sodium chloride; or if the syntan is prepared by condensing a sodium naphthalene sulfonate after acidification with sulfuric acid the sodium sulfate produced may replace the corresponding amount of salt. It will be found that the tan is adjusted to acidity of about pH 1.3, the acidification being preferably effected by means of the formic acid in order to prevent the presence of undue quantities of strong mineral acid.

The syntan may then be used in tanning, for example, by mixing 15 parts of sumac extract, 6 parts of the syntan, and 4 parts of salt with enough water to make up 150 parts by volume. When this solution is used for tanning 20 to parts by weight of sheep skin sklvers by tumbling for 2 hours, washing in running water and drying on a board, grain side up, a very light colored, practically white leather is obtained with no substantial disintegration of cellular structure of the h de and the color is materially lighter and 55 standard commercial disulfodinaphthyl methane syntan.

What I claim is:

l. A'tanning and bleaching compositioncomprising a synthetic tanning agent of the sulfonated diarylmethane type and formic acid.

2. A tanning and bleaching composition comprising a synthetic tanning agent of the disulfodinaphthylmethane type and formic acid.

3. A tanning and bleaching composition comprising a synthetic tanning agent of the sulfonated diarylmethane type containing 'free sulfonic acid groups and formic acid in amounts sufllcient to offset the corrosive action of said free sulfonic acid on hides and leather.

4. A tanning and bleaching composition comprising a synthetic tanning agent of the disulless sensitive to light than leather tanned with a fodinaphthylmethane type containing free sulfonic acid groups and formic acid in amounts suflicient to offset the corrosive action of said free sulfonic acid on hides and leather.

5. A process of preparing a tanning and bleach: ing composition from synthetic tans of the type containing free sulfonic acid groups which comprises neutralizing said free sulfonic acid with alkali to a point where its corrosive action on hides is substantially overcome, and adding formic acid in amounts sufficient to lower the pH to the desired value for use.

6. A process of preparing a tanning and bleaching composition which comprises neutralizing a disulfodiarylmethane by addition of alkali, liberating free sulfonic acid groups by adding mineral acid, and adding formic acid.

ALPHONS O. JAEGER.

CERTIFICATE OF CORRECTION.

atent No. 2,051 ,60'7.

ed patent was erroneously descri Corporation" whereas said name 3 American Cyanamid & Chemical Corporation, Delaware, as shown by the records of assign the said Letters Patent s the samesmay conform to the record 0 Signed and sealed this 2nd day of February,

August 18, 1956.

ALPHONS o. JAECER.

It is hereby certified that the name of the assignee in the above number (Seal) bed and specified as "Cyanamid 8: Chemical hould have been described and specified 'as New York, N. Y. a corporation of ments in this office; and that hould be read with this correction therein that f the case in the Patent Office.

I Leslie Frazer Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 2,051,607. August 18, 1936.

ALPHONS o. JAEGER.

I It is hereby certified that the name of the assignee in the above number ed patent was erroneously described and specified as "Cyanamid 8: Chemical Corporation" whereas said name should have been described and specified as American Cyanamid 8: Chemical Corporation, New York, N. Y. a corporation of Delaware, as shown by the records of assignments in this. office; and that the said Letters Patent should be read with this correction therein that the same-may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of February, A. D. 1937.

Leslie Frazer (Seal) Acting Commissioner of Patents. 

